Battery-voltage indicator of camera

Abstract

In a voltage indicator of a camera, the voltage value of the battery is converted into digital value through analog-to-digital conversion processing. Such digital signals are digitally expanded by converting equal difference variations thereof into equal ratio variations thereof. The digitally expanded signals are adapted to vary in accordance with variations of the battery voltage. Thus, the expanded digital signals energize an alarm to audibly indicate the value of the battery voltage.

What is claimed is: 
     
       1. A battery-voltage indicator of a camera comprising: a battery, the voltage of which is to be checked;   said battery for being employed as the power source of circuitry means necessary for the photographing operation;   an analog-to-digital converter for changing the analog value of a battery voltage into digital signal;   said analog-to-digital converter including an integrator being connected to said battery and counter means for counting digital value on operation of the integrator, in accordance with the voltage value of the battery;   an expanding circuit for enlarging the period of the digital output of said converter, wherein said expanded digital output is adapted to vary its period in accordance with variations of the battery voltage; and   indicator means for indication of the voltage value of said battery by means of the output of said expanding circuit.   
     
     
       2. A battery-voltage indicator of a camera according to claim 1, said analog-to-digital converter further including switching means for selectively connecting the battery voltage and a reference voltage to the integrator for integration. 
     
     
       3. A battery-voltage indicator of a camera according to claim 2, said analog-to-digital converter further including a comparator connected to said integrator and a latching circuit for latching the counting output of the converter in response to the output of said comparator. 
     
     
       4. A battery-voltage indicator of a camera according to claim 3, wherein said switching means is adapted to firstly connect the battery voltage to said integrator and then the reference voltage to the same at a predetermined counting value of said counter; said reference voltage causing the integrator to integrate down. 
     
     
       5. A battery-voltage indicator of a camera according to claim 4, wherein said latching circuit operates to latch the output counting value of said counter during said integration down of the integrator. 
     
     
       6. A battery-voltage indicator of a camera according to claim 5, wherein said analog-to-digital converter is constituted as a dual-slope integrator A/D converter. 
     
     
       7. A battery-voltage indicator of a camera according to claim 1, wherein said indicator means is constituted as an acoustic device for producing signal sounds which indicates the voltage value of said battery. 
     
     
       8. A battery-voltage indicator of a camera according to claim 7, wherein said digital expanding circuit is adapted to chop an audio frequency signal for actuating said acoustic device by means of the period of the output thereof. 
     
     
       9. A battery-voltage indicator of a camera according to claim 1, wherein said digital expanding circuit includes a pulse forming circuit for producing such pulses that frequency varies in multiple-series and a pulse selecting circuit for selecting pulses with a frequency to be selected, in response to an output of said analog-to-digital converter. 
     
     
       10. A battery-voltage indicator of a camera according to claim 1, wherein said digital expanding circuit, functions as an expanding circuit in a shutter speed controlling circuit. 
     
     
       11. A battery-voltage indicator of a camera according to claim 1, wherein said integrator is commonly used to integrate an output corresponding to shutter time value in the exposure controlling mode. 
     
     
       12. A battery-voltage indicator a camera comprising: a battery for use as the power source of circuitry means necessary to photographing operations;   an acoustic device for audibly indicating voltage variations of said battery with discontinuous sounds which is adapted to vary its interval in accordance with said voltage variations;   an analog-to-digital converter for converting the analog value of a battery voltage into digital value; and   circuit means for converting equal difference variations of said digital value of the output signals of said converter into equal ratio variations in order to expand said output signals of converter, wherein said acoustic device is energized by said expanded output signals to indicate the voltage value of the battery.   
     
     
       13. A battery-voltage indicator of a camera comprising: a battery, the voltage of which is to be checked;   said battery for being employed as the power source of circuitry means necessary for a photographing operation;   an analog-to-digital converter for changing the analog value of a battery voltage into a digital signal and for changing the analog value of the exposure value into a digital value;   an expanding circuit connected to the output of the converter for enlarging the period of the digital output of the converter, wherein said expanded digital output varies its period in accordance with variations of the battery voltage; and   indicator means responsive to the output of said expanding circuit for indication of the voltage value of said battery.   
     
     
       14. A battery-voltage indicator of a camera comprising: a battery, the voltage of which is to be checked;   said battery for being employed as the power source of circuitry means necessary for a photographing operation;   an analog-to-digital converter for changing the analog value of a battery voltage into a digital pulse train signal output, the number of pulses being determined in accordance with the value of the battery voltage;   an expanding circuit connected to the output of the converter for enlarging the period of the digital signal output of the converter, wherein said expanded digital signal output has its period vary in accordance with variations of the battery voltage, wherein said digital expanding circuit operates as an expanding circuit in a shutter speed controlling circuit; and   indicator means responsive to the output of said expanding circuit for indication of the voltage value of said battery.   
     
     
       15. A battery-voltage indicator of a camera comprising: a battery, the voltage of which is to be checked;   said battery for being employed as the power source of circuitry means necessary for a photographing operation;   an analog-to-digital converter for changing the analog value of a battery voltage into a digital pulse train signal output, the number of pulses being determined in accordance with the value of the battery voltage;   an expanding circuit connected to the output of the converter for enlarging the period of the digital signal output of the converter, wherein said digital expanding circuit includes a pulse forming circuit for producing such pulses that frequency varies in multiple-series and a pulse selecting circuit for selecting pulses with a frequency to be selected, in response to an output of said analog-to-digital converter, wherein said expanded digital signal output has its period vary in accordance with variations of the battery voltage; and   indicator means responsive to the output of said expanding circuit for indication of the voltage value of said battery.   
     
     
       16. A battery-voltage indicator of a camera comprising: a battery, the voltage of which is to be checked;   said battery for being employed as the power source of circuitry means necessary for a photographing operation;   an analog-to-digital converter for changing the analog value of a battery voltage into a digital pulse train signal output, the number of pulses being determined in accordance with the value of the battery voltage;   an expanding circuit connected to the output of the converter for enlarging the period of the digital signal output of the converter, wherein said expanded digital signal output has its period vary in accordance with variations of the battery voltage; and   indicator means responsive to the output of said expanding circuit for indication of the voltage value of said battery.